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Emissions to air

Dust, emissions and odours arising from a site can cause many adverse health, environmental and economic impacts.

• Emissions to air can seriously effect the health of site staff and neighbours.
• Dust and emissions can harm local wildlife and pollute watercourses. They can be unsightly, odourous and the effects can take years to reverse.
• Both of the above can lead to fines or imprisonment which can up project costs and halt construction.

Why dust, emission and odour good practice is important

Dust, emissions and odours disturb site neighbours. For example, annoyance is caused when residents have to re-clean washing that has been hanging out and when they have to wash cars, curtains and windows. Windblown dust can be unsightly over long distances in scenic areas. In exceptional circumstances, dust can affect health by, for example, causing eye irritation. Asthma can be exacerbated by exposure to respirable dust.

Dust is generally considered to be any airborne solid matter up to about 2 mm in size. Particle sizes can vary considerably, depending on their origin, and the smallest particles can be breathed in. Some dust, such as limestone dust, is chemically active.

Key issues include

• Very low concentrations of dust can affect plant and fruit growth. Plant growth is especially susceptible to dusts that are highly alkaline, for example limestone, and cement dust. The extent of effects caused is weather-dependent. For example, ash trees may drop their leaves up to six to eight weeks early following exposure to high levels of dust.
• Dust can damage plants and animals and their habitats, particularly if they are sensitive.
• Within the site, dust can cause mechanical or electrical faults to equipment such as computers and will increase abrasion of moving parts in plant and clogging of filters.

Examples of good practice

With dust, emissions and odour there are usually no imposed standards to be met for a particular contract. Regulators generally only become involved once problems have been created and complaints received.

The most effective application of water in suppressing dust is by using a fine spray, but the efficiency depends on the speed of the bowser. Repeat spray regularly and frequently, especially during warm and sunny weather when water will evaporate quickly. Ensure that any runoff of water from this process is controlled properly.

Picture: Bowsers can be used to keep exposed earth damp and prevent dust generation.

Effective planning and management of dust control requires knowledge of wind conditions for the site. Although prevailing winds across most of the country are from the south-west, there are regional and seasonal variations. For example, in winter months winds are often from the north-east. General historical wind data for the site locality can provide guidance on the likely wind speed and direction. This can be obtained from the Meteorological Office in Exeter in the form of wind roses. Wind roses summarise the occurrence of winds at a location, showing their strength, direction, and frequency.

If dust-generating activities cannot be avoided, it may help to erect screens to act either as windbreaks or as dust screens. These can take the form of permeable or semi-permeable fences, but be aware that they can be expensive if designed to resist high winds. Trees or shrubs planted early as part of site landscaping can provide some screening; likewise retention of existing vegetation (or buildings to be demolished) will aid screening.

Dust is generally considered to be any airborne solid matter up to about 2mm in size. Particle sizes can vary considerably, depending on their origin, and the smallest particles can be breathed in. Some dust, such as limestone dust, is chemically active.

Checklist - preventing dust

Haul routes

• Select suitable haul routes away from sensitive areas if possible.
• Pave heavily used areas, or use geotextiles (eg around batching plant or haul routes).
• Provide a length of paved road before the exit from the site.
• Reduce the width of haul roads (while still allowing two-way traffic) to minimise surface area from which dust may be produced.
• Sweep paved access roads (whilst still allowing two-way traffic) and public roads regularly using a vacuum sweeper.
• Limit vehicle speeds - the slower the vehicles the less the dust generation.
• Damp down and ensure that any associated run off is properly controlled.

Demolition

• Use enclosed chutes for dropping to ground level demolition materials that have the potential to cause dust and regularly dampen the chutes.
• The use of mobile plant for crushing materials such as bricks, tiles and concrete is covered by the EPA 1990.
• Locate crushing plant away from sensitive sites - consider siting within buildings (eg buildings within the site that will not be demolished or those to be demolished last).

Plant

• Clean the wheels of vehicles leaving the site so that mud is not spread on surrounding roads - dry mud turns to dust.
• Ensure that exhausts do not discharge directly at the ground.

Earthworks and excavations

• Re-vegetate or seal temporary or completed earthworks as soon as possible.
• Keep earthworks damp - try to programme to avoid exceptionally dry weather.

Materials handling and storage

• Locate stockpiles of fine grained material out of the wind (or provide wind breaks) to minimise the potential for dust generation.
• Keep the stockpiles to the minimum practicable height and use gentle slopes.
• Compact and bind stockpile surfaces (in extreme cases).
• Re-vegetate long-term stockpiles.
• Minimise the storage time of materials on site.
• Store materials away from the site boundary and downwind of sensitive areas.
• Ensure that all dust-generating materials transported to and from site are covered by tarpaulin.
• Minimise the height of fall of materials.
• Avoid spillage, and clean up as soon as possible.
• Damp down and ensure that any associated run off is properly controlled.

A company was fined £8500 under air pollution legislation for twice carrying dusty material in uncovered containers for a short distance on a public road.

Concrete batching and pouring

• Mix large quantities of concrete or bentonite slurries in enclosed/shielded areas.
• Before concrete pours, vacuum dirt in form work rather than blowing it out.
• Keep large concrete pours clean after they have gone off. They generate large quantities of dust.

Cutting/grinding/grouting/packing

• Minimise cutting and grinding on site.
• On cutters and saws, use equipment and techniques such as dust extractors to minimise dust. Consider a wet cutting saw or use vacuum extraction.
• Spray water during cutting of paving slabs to minimise dust and ensure that any associated run off is properly controlled.

Checklist - preventing emissions and odours

• Keep vehicles and plant used on site well maintained and regularly serviced. Ensure that all vehicles used by contractors comply with MOT emissions standards at all times.
• Control deliveries to site, to minimise queuing.
• Make sure that engines are switched off when they are not in use.(This is particularly important in summer near buildings that do not have air conditioning.)
• Control staff car parking to minimise queuing and switch off engines when vehicles are not in use.
• Keep refuelling areas away from the public.
• Do not burn waste materials/tyres on site.
• Use covered containers for organic waste and remove frequently.
• Remove organic waste (eg weeds and other vegetation) before it begins to decompose.
• Store fuels and chemicals and other dangerous substances in the appropriate manner.
• Take account of the wind conditions when arranging activities that are likely to emit aerosols, fumes, odours and smoke.
• Position site toilets away from public areas.
• Use pre-agreed transport routes.
• Minimise queuing by controlling deliveries to site.
• Keep site vehicles and plant well maintained and regularly serviced.
• Ensure that vehicles comply with MOT emissions standards.
• Keep refuelling areas away from the public.
• Do not burn any waste on site.
• Use covered containers for wastes and empty frequently.
• Take account of the wind conditions when arranging activities that are likely to emit aerosols, fumes, odours and smoke.

Key references:

• CIRIA C650 Environmental good practice on site.
• Environmental impacts of surface mineral workings, DETR, HMSO.
• Secretary of State's Guidance - Mobile Crushing and Screening Processes, 1996, Department of Environment, PG3/16(96).

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